I. Field of the Invention
This invention relates to a process for the production of high octane motor gasoline components, and other fuels. In particular, it relates to a process for the production of high octane motor gasoline, or high octane motor gasoline components, from highly aromatic mid distillate product streams, or streams which contain high concentrations of multi-ring aromatic or hydroaromatic compounds, whether derived from petroleum or synthetic sources, or both.
II. Background and Prior Art
Usually more than one-half of every barrel of petroleum crude that is processed in a modern refinery is converted into motor gasolines. Motor gasolines are produced from a blending pool of streams obtained from many different refinery processes, primarily from catalytic reforming and alkylation processes. Motor gasolines are constituted principally of complex mixtures of paraffins, naphthenes, olefins and aromatic hydrocarbons, which generally boil within a range of from about C.sub.5.sup.+ -430.degree. F. (20.degree.-225.degree. C.). Improved engine performance demands significantly improved motor gasoline octane requirements. Due to restrictions on the use of alkyl lead compounds, with the ultimate projection which will require prohibition of the use of such compounds in gasolines altogether, refiners are taxed in their ability to produce high octane blending components. Consequently there is a demand upon refiners to find ways and means of increasing the octane number levels of their motor gasoline pools.
Catalytic cracking, or "cat cracking," is another refinery process for producing major quantities of motor gasoline. It also suffers a major deficiency however in that it produces large quantities of highly aromatic light cat cycle oil (LCCO) due to the high temperature of the operation. The LCCO, having an API gravity of 10-15, is difficult to market for which reason it is often hydrogenated and then blended with kerosene (a jet fuel stock) to increase its API gravity (to 30 API) so that the product can be sold as heating oil. A relatively high value product is thus used up, and depreciated in value, to make the LCCO a marketable product. LCCO, after hydrogenation, is also added to automotive diesel fuel and the product sold as automotive diesel fuel, but such manner of disposing of the LCCO is necessarily limited. Whereas conventional hydrogenation processes might be used to upgrade the LCCO this is not practical because excessive hydrogen consumption is required to increase the cetane and gravity to meet diesel specifications. On the other hand, catalytic hydrocracking processes are not efficient in producing motor gasoline blending components because these processes produce a hydrogen-rich motor gasoline component which first must be reformed before it can meet octane specifications. This, of course, adds to the cost of octane values obtained from catalytic hydrocracking processes. Additionally, conventional hydrocracking catalysts crack paraffin molecules into lower boiling paraffins which effectively reduces the octane value of the product.
Highly aromatic mid distillate streams are also available from synthetic fuel processes, e.g., coal liquification processes, and steam cracking operations for the production of olefins, e.g., steam cracker light gas oil. The product streams derived from these processes, and the problems associated with the disposition of these products is closely akin to those described above for the disposition of petroleum stocks.
In U.S. application Ser. No. 760,894, supra, there is described a process for the production of gasoline from feeds characterized as mixtures of fused two-ring aromatic and hydroaromatic hydrocarbons which are reacted with hydrogen, over a catalyst characterized as elemental iron and one or more alkali or alkaline-earth metal components at temperatures ranging about 225.degree. C. to 430.degree. C. The feed is selectively hydrogenated and hydrocracked over the iron catalyst to produce a lower molecular weight high octane product. Whereas this process represents a meritorious advance in the state of the art much of the gasoline product resultant from this process is of lesser octane than desirable due to contamination of the product with low octane refractory components included in the feed. In addition, it is now recognized that in this process the levels of conversion of the mixed fused two-ring aromatic and hydroaromatic hydrocarbons to molecular species useful as gasoline blending components is relatively low. Many of the molecular species found in available feed streams, whether from petroleum or synthetic sources, notably paraffins and naphthenes, simply do not react over the iron catalyst. Moreover, other molecular species of these mixtures, notably aromatic hydrocarbons having three rings and greater in the molecule, react in a manner detrimental to the life of the catalyst. Other species consume too much hydrogen and produce end products of no greater value, or of lesser value, than the molecular species originally present in the feed.
There presently exists a pressing need for a further improved process useful for the conversion to lower boiling hydrocarbons of higher octane levels suitable for direct use in gasoline, or as motor gasoline blending components, or diesel fuel, or both, of highly aromatic mid distillates derived from cat cracking petroleum stocks (such as light cat cycle oil; or the heavy hydrocrackate thereof), liquifaction of coal or the hydroconversion of heavy feeds (such as bitumen, tar sands, etc.) which contain high concentratios of multi-ring aromatic or hydroaromatic compounds.
III. Objects
It is, accordingly, the primary object of this invention to fill this and other needs.
In particular, it is an object of this invention to provide a process for the conversion of highly aromatic mid distillates, e.g., LCCO, or LCCO and related fuel fractions such as those obtained from synthetic and chemicals operations, or admixtures of such fuel factions, into lower boiling, high octane gasolines or motor gasoline blending components.
A specific object is to provide a process for the conversion of highly aromatic mid distillates, e.g. LCCO, or LCCO and said related fuel fractions, or admixtures of such fuel fractions, to motor gasoline of higher octane, or to high octane motor gasoline blending components.
A further, and yet more specific object, is to provide a process for the treatment of feed fractions from conventional or synthetic sources, or both, containing fused two-ring aromatic and hydroaromatic hydrocarbons of selected boiling range to coproduce, on reaction of the feed, with hydrogen, over an iron catalyst as described in U.S. Ser. No. 760,894, supra, a higher octane gasoline, and mid distillate useful as a diesel fuel, or diesel and/or jet fuel blending stock.